Screen assembly for a vibrating screening machine

ABSTRACT

According to one aspect there is provided a screen assembly for a vibrating screening machine. The screen assembly comprises a screen chassis and a screen for screening material such as a solution containing liquid and solids. The screen chassis comprises a first face and a second face opposite to the first face, the screen chassis defining a plurality of openings therethrough from the first face to the second face for allowing passage of a material that has been screened. The screen is attached to the first face of the screen chassis and covering the openings of the screen chassis at the first face. The screen chassis may be made of a light-weight, stiff material. The screen may be made of a durable material such as metal. A method for making a screen assembly is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase entry under 35 U.S.C. § 371 ofInternational Patent Application PCT/CA2015/051372, filed Dec. 23, 2015,designating the United States of America and published in English asInternational Patent Publication WO 2016/106450 A1 on Jul. 7, 2016,which claims the benefit under Article 8 of the Patent CooperationTreaty to U.S. Provisional Patent Application Ser. No. 62/098,529, filedDec. 31, 2014, the disclosure of each of which is hereby incorporatedherein in its entirety by this reference.

FIELD OF THE DISCLOSURE

The present invention relates to vibrating screening systems for theseparation of solids and fluids, particularly to screen assemblies forsuch systems.

BACKGROUND

Drilling and mineral extraction processes in various industries,including the mining and oil industries, often produce slurries ofsolids and liquids that must be separated from one another. Screeningmachines are used to separate such solids and liquids. For example,screen assemblies (such as shaker screen assemblies) may be used toseparate drill cuttings from drilling fluid. A screening machinetypically includes a screen bed, comprised of individual screenassemblies, over which a material (e.g. slurry or another solution)containing fluids and solids is passed, and which is then subjected tovarious separation forces including gravity and shaking.

However, as the combined weight of screen assemblies and the materialloaded on a screening machine increases, the g-force provided by thescreening machine to the material decreases in an apparently linearrelationship. Furthermore, as the g-force at the center of the screenincreases, the center of the screen may oscillate at a rate higher thanthe oscillation rate of the vibrating machine, which in turn mayincrease the rate of wear of the screen assembly. For example, suchoscillations in the center of the screen assembly may cause a metal meshof the screen to wear out at an increased rate. Therefore it isdesirable to use lighter screen assemblies to reduce the direct loadingof the screening machine and allow for a more optimized performance.

Conventional screen assemblies may be partially composed of plastic(such as polyurethane), but such conventional screen modules typicallyshow little or no weight decrease over conventional metal screenmodules. Such modules generally include metal tubing that is combinedwith plastic, in order to provide a structure with enough rigidity toovercome inertial issues when the screen module is subjected tofrequency, amplitude, and mass forces present in a vibrating screeningmachine.

Current fabrication techniques may be labour intensive, and thusexpensive. The welding of conventional screen frames may be inherentlyprone to quality issues such as warping of the frame itself.Furthermore, conventional screen assemblies (e.g. including weldedframes) may not be easily recyclable or reusable.

SUMMARY

According to one aspect, there is provided a screen assembly for avibrating screening machine, the screen assembly comprising: a screenchassis comprising a first face and a second face opposite to the firstface, the screen chassis defining a plurality of openings therethroughfrom the first face to the second face for allowing passage of amaterial that has been screened; a screen for screening the material,the screen being attached to the first face of the screen chassis andcovering the openings of the screen chassis at the first face.

In some embodiments, the screen comprises a perforated plate.

In some embodiments, the perforated plate is formed from sheet metal.

In some embodiments, the screen comprises a frame and a screening layer,the frame defining at least one opening, the at least one opening atleast partially overlaying the openings of the screen chassis, the framebeing attached to the screen chassis, the screening layer covering theat least one opening of the frame.

In some embodiments, the screening layer comprises a mesh.

In some embodiments, said at least one opening of the frame comprises aplurality of openings that are aligned with the openings of the screenchassis.

In some embodiments, the screen comprises metal.

In some embodiments, the frame is formed from sheet metal.

In some embodiments, the screen chassis comprises one or more of:plastic; aluminum; steel; and a composite material.

In some embodiments, the screen chassis is formed by a molding process.

In some embodiments, the first face of the screen chassis facessubstantially upward when the screen assembly is mounted in thevibratory screening machine.

In some embodiments, the screen chassis comprises a grid structuredefining the plurality of openings in the screen chassis.

In some embodiments, the grid structure of the screen chassis comprisesa plurality of ribs parallel to the first and second faces, and aplurality of cross ribs parallel to the first and second faces andperpendicular to the ribs.

In some embodiments, one or more of the ribs or cross ribs extendbetween the first face and the second face of the screen chassis.

In some embodiments, one or more of the ribs and cross ribs extend onlypart way from the first face of the screen chassis toward the secondface.

In some embodiments, the frame of the screen comprises a grid structurethat is aligned with the grid structure of the screen chassis.

In some embodiments, the screen assembly further comprises a secondscreen for screening the material, the second screen being attached tothe second face of the screen chassis and covering the openings of thescreen chassis at the second face.

In some embodiments, the second screen comprises: a second framedefining at least one opening; and a second mesh covering the at leastone opening of the second frame.

In some embodiments, the screen chassis defines a plurality of channelsallowing solids caught by the second screen to move through saidchannels.

In some embodiments, the screen assembly further comprises a secondscreen for screening the material, the second screen being attached tothe second face of the screen chassis and covering the openings of thescreen chassis at the second face, and said one or more of the ribs andcross ribs extending only part way from the first face of the screenchassis toward the second face allow passage thereunder of solids caughtby the second screen, and said one or more of the ribs or cross ribsextending between the first face and the second face of the screenchassis form channels therebetween for passage of said solids caught bythe second screen.

In some embodiments, the screen assembly further comprises at least oneopen side allowing said solids caught by the second screen to exit fromof the at least one open side.

In some embodiments, the screen attached to the first face of the screenchassis has a first mesh size or perforation size, and the second screenhas a second mesh size or perforation size.

In some embodiments, the first mesh size or perforation size isdifferent than the second mesh size or perforation size.

In some embodiments, the first mesh size or perforation size is largerthan the second mesh size or perforation size.

In some embodiments, the second screen is removably attached to thescreen chassis such that the screen assembly has a single screenconfiguration in which the second screen is not attached to the screenassembly, and a dual screen configuration in which the second screen isattached to the screen assembly.

In some embodiments, a second screen is removably attachable to thesecond face of the screen chassis such that the second screen covers theopenings of the screen chassis at the second face and such that thescreen assembly has a single screen configuration in which the secondscreen is not attached to the screen assembly, and a dual screenconfiguration in which the second screen is attached to the screenassembly.

In some embodiments, the screen assembly further comprises a frameattached to the second face of the screen chassis, the frame attached tothe second face defining at least one opening at least partiallyoverlaying the openings of the screen chassis at the second face.

In some embodiments, the screen is removably attached to the screenchassis such that the screen or the screen chassis is replaceable.

In some embodiments, the screen chassis is a first screen chassis, andthe screen assembly further comprises at least one additional screenchassis having openings therethrough, said first screen chassis and saidat least one additional screen chassis being in a stacked formation withthe openings of the first screen chassis being aligned with the openingsof the at least one additional screen chassis, the screen assemblyfurther comprising, for each pair of adjacent screen chassis, arespective additional screen, for screening the material, between saidpair of adjacent screen chassis.

According to another aspect, there is provided a screen chassis forattaching to a screen and for use in a vibratory screening machine, thescreen chassis comprising: a first face and a second face opposite tothe first face, the screen chassis defining a plurality of openingstherethrough from the first face to the second face for allowing passageof a material.

In some embodiments, the screen chassis comprises one or more of:plastic; aluminum; steel; and a composite material.

In some embodiments, the screen chassis comprises a grid structuredefining said openings.

In some embodiments, the grid structure of the screen chassis comprisesa plurality of ribs parallel to the first and second faces, and aplurality of cross ribs parallel to the first and second faces andperpendicular to the ribs.

In some embodiments, the screen chassis is removably attachable to asecond screen at the second face of the screen chassis such that thesecond screen covers the openings of the screen chassis at the secondface.

In some embodiments, the screen chassis is removably attachable to saidscreen such that the screen or the screen chassis is replaceable.

According to another aspect, there is provided a screen for attaching toa screen chassis and for screening a material, the screen chassiscomprising openings, the screen comprising: a frame comprising aplurality of openings that align with the openings in the screen chassiswhen the screen is attached to the screen chassis; and a mesh forscreening a material, the mesh covering the openings of the frame.

In some embodiments, the screen is removably attachable to the screenchassis such that the screen or the screen chassis is replaceable.

In some embodiments, the screen comprises metal.

In some embodiments, the screen is at least partially formed from sheetmetal.

According to another aspect, there is provided a method of making ascreen assembly comprising: providing a screen chassis, the screenchassis comprising a first face and a second face opposite to the firstface, the screen chassis defining a plurality of openings therethroughfrom the first face to the second face for allowing passage of amaterial that has been screened; providing a screen for screening thematerial; and attaching the screen to the screen chassis such that thescreen covers the openings in the screen chassis.

In some embodiments, providing the screen chassis comprises forming thechassis by a molding process.

In some embodiments, the screen comprises at least one of a frame and aperforated plate, and providing the screen comprises forming said atleast one of the frame and the perforated plate by a sheet metalpunching process.

In some embodiments, the method further comprises attaching a secondscreen to the second face of the screen chassis such that the screencovers the openings in the screen chassis at the second face.

In some embodiments, the second screen is removably attached to thesecond face of the screen chassis.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art, upon review of the followingdescription of example embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tothe accompanying diagrams, in which:

FIG. 1 is a top perspective view of a single screen assembly accordingto one embodiment;

FIG. 2 is a bottom perspective view of the single screen assembly ofFIG. 1;

FIG. 3 is a bottom perspective view of a plastic chassis of the screenassembly shown in FIGS. 1 and 2;

FIG. 4 is a top plan view of the chassis shown in FIG. 3;

FIG. 5 is a bottom plan view of the chassis of FIGS. 3 and 4;

FIG. 6 is a cross-section view of the chassis of FIG. 5, taken along theline B-B shown in FIG. 5

FIG. 7 is a cross-section view of the chassis of FIG. 5, taken along theling C-C shown in FIG. 5;

FIG. 8 is an enlarged cross-section view of a portion of the chassiswithin circle E in FIG. 7;

FIG. 9 is an exploded view of the screen assembly from FIGS. 1 and 2,but with the addition of a second metal screen to form a dual screenassembly;

FIG. 10 is a top perspective view of a dual screen assembly according toanother embodiment;

FIG. 11 is a bottom perspective view of the screen assembly of FIG. 10;

FIG. 12 is a bottom plan view of the screen assembly of FIGS. 10 and 11;

FIG. 13 is a cross section view of the screen assembly of FIG. 12 takenalong the line A-A shown in FIG. 12;

FIG. 14 is an enlarged view of the portion of the screen assembly withinthe circle D in FIG. 13;

FIG. 15 is a top perspective view of a single screen assembly accordingto yet another embodiment;

FIG. 16 is a bottom perspective view of the screen assembly of FIG. 15;

FIG. 17 is a top plan view of a chassis of the assembly shown in FIGS.15 and 16;

FIG. 18 is a bottom plan view of a chassis of FIG. 17;

FIG. 19 is an enlarged partial cross sectional view of the chassis ofFIG. 18 taken along the line D-D in FIG. 18;

FIG. 20 is a side view of the chassis of FIGS. 17 and 18;

FIG. 21 is a top plan view of an upper metal screen of the screenassembly shown in FIGS. 15 and 16;

FIG. 22 is a bottom plan view of a lower metal frame of the screenassembly shown in FIGS. 15 and 16;

FIG. 23 is a top plan view of the assembled screen assembly of FIGS. 15and 16;

FIG. 24 is a cross section side view of the screen assembly of FIG. 24taken along the line L-L in FIG. 23;

FIG. 25 is a cross section top view of the screen assembly of FIG. 24taken along the line P-P in FIG. 24;

FIG. 26 is a cross section bottom view of the screen assembly of FIG. 23taken along the line R-R in FIG. 24;

FIG. 27 is an exploded view of a stacked screen assembly according toyet another embodiment;

FIG. 28 is perspective view of stacked screen assembly of FIG. 27, asassembled;

FIG. 29 is a flowchart of a method accordance to some embodiments; and

FIG. 30 is a top view of a metal frame according to another embodiment.

DETAILED DESCRIPTION

According to some embodiments, there is provided a screen assembly (suchas a shaker screen assembly) including a screen chassis to which isattached at least one screen for screening material (such as a solutionor slurry containing solids and liquids). The screen chassis has a firstface and a second face opposite to the first face, and the screenchassis defines a plurality of openings therethrough from the first faceto the second face for allowing passage of the material (e.g. slurry)that has been screened. The screen is attached to the first face of thescreen chassis and covers the openings of the screen chassis at thefirst face.

The screen may include a frame and a screening layer (e.g. a mesh)covering at least one opening in the frame. Alternatively, the screenmay include a perforated plate and may not include a frame. The screenmay be made at least partially formed of metal, such as sheet metal. Forexample the frame (or perforated plate) may be formed of sheet metal. Asheet metal perforated plate or frame for a screen may be substantiallyflat on a face of the chassis, or may also be folded over one or moresides of the chassis to add additional structural strength to theassembly. The screen may provide wear resistance for surfaces exposed toa material (e.g. a solution such as slurry) to be screened, while thechassis may be made of a light, stiff material to allow for alightweight screen assembly. Such a design may reduce the weight of thescreening screen assembly to as little as 30-50% of conventional modulescurrently in use which have frames made of metal and/ormetal-tube-reinforced plastic.

The screen may, for example, be made from any metal that can withstandabrasion and wear by materials to be screened, including but not limitedto steel and stainless steel. The metal screen may be at least partiallyformed from sheet metal. For example, a sheet metal punching process(e.g. using a CNC punch machine) may be used to make a perforated plateor a frame of the screen. In other embodiments, the screen is not madeof metal. Other possible materials for the screen include, but are notlimited to ceramics and plastics such as polyurethane. Embodiments arenot limited to any particular material for the screen.

The screen chassis may comprise a hard, lightweight material such ashard plastic, aluminum, composite materials (e.g. carbon fiber), etc.For example, the chassis may be formed of a glass filled polypropylene,which may provide strength, temperature and chemical resistance for usein a vibratory screening machine. One possible glass filledpolypropylene is a composite of polypropylene and glass fiber (e.g. 20%glass fiber). Other materials such as steel may also be used.Embodiments are not limited to any particular material for the screenchassis. The chassis may be formed by any known method, including butnot limited to molding.

The screen may be attached to the screen chassis by any method known inthe art, including but not limited to staking (e.g. heat staking)mechanical fasteners or chemical adhesives. Alternatively, the screenmay be attached to the screen chassis during the molding process, forexample by insert molding or overmolding. The screen may be removablyattached such that the screen and/or the screen chassis is replacable.

In some embodiments, the chassis is molded and the screen (or the frameof the screen) is made by punching sheet metal. Production of a moldedchassis and punched sheet metal may be machine automated and thus morecontrollable than a conventional process of welding a frame. Thisautomated production may, therefore, reduce variability in the formand/or structural integrity of the screen assemblies. The screen and/orscreen chassis may be replaceable, which may improve the potential forrecycling and reusability of the screen assembly. For example, a screenmay be removably attached to a screen chassis, and a single chassis maybe thereby used with multiple different screens (e.g. the screens may beswappable). Similarly, a single screen may be used with multiple screenchassis.

The screen assemblies described herein may also possibly include ceramicmaterials (e.g. in the chassis and/or screen) to not only provideenhanced life but changes in the surface tension between the filteringmaterial and the the fluids being separated.

The screen may have a grid-like frame and a mesh. The grid-like framemay define openings which are covered by the mesh. The frame and mesh ofthe screen may, for example, be metal. The metal mesh may be attached tothe metal frame of the metal screen by an adhesive, including but notlimited to epoxy. The screen chassis can have a grid-like frame so thatopenings in the grid align with the frame of the metal screen. Thescreen chassis can be attached to a single screen (e.g. metal screen) onone face of the grid, or can be attached to two screens (e.g. metalscreens), each on opposite faces of the grid.

In use, the screen assembly may be oriented substantially horizontally,or at a slight angle to the horizontal, with the screen facingsubstantially upwards, so that the material (e.g. slurry) to be screenedcan fall onto the module to contact the screen. Larger solids may beretained by a mesh or perforated surface of the screen, and smallersolids will pass through the screen and through the openings in the gridof the plastic chassis under the influence of gravity. The term “meshsize” is used herein to denote the size of openings in the mesh. Theterm “perforation size” refers to the size of holes or openings in aperforated surface such as a perforated plate. Thus, the mesh size orperforation size determines the size of solids that can pass through themesh or the perforated surface.

In a dual screen module in which two opposing faces of the screenchassis are each attached to a different screen, the screens can havethe same or different mesh sizes or perforation sizes. The screen on theupper face of the module which first contacts the material or slurry tobe screened may have a larger mesh size or perforation size, so as toscreen out the largest solids and allow mid-size and smaller solids topass through. The screen on the lower face of the module which contactsthe material or slurry which passes through the upper screen may have asmaller mesh size or perforation size, so that it can selectively retainsolids which are small enough to pass through the upper screen.

FIGS. 1 and 2 are, respectively, top and bottom perspective views of asingle screen assembly 100 according to one embodiment. The screenassembly 100 may, for example, be a shaker screen assembly for avibrating screen machine. The screen assembly 100 includes a chassis 102and a screen 104 attached thereto. The chassis 102 is made of hardplastic in this embodiment, although other materials (e.g. lightweightand stiff materials) may also be used as described above. The screen 104in this embodiment is made of metal although other materials may be usedfor the screen in other embodiments, as described above. The metalscreen 104 may be manufactured at least partially from sheet metal.

As will be explained in more detail below, the screen chassis 102defines a plurality of openings 120 therethrough to allow passage ofmaterial that has been screened. The metal screen 104 includes a frame142 that defines a plurality of openings 144, and a mesh (not shown)covers the openings 144. The openings 144 of the frame 142 are generallyaligned to the openings 120 of the chassis 102. The openings 144 alsohave a size and shape that generally correspond to the openings 120 ofthe screen chassis 102, although the size and/or shape of openings in aframe may not correspond to the size and/or shape of individual openingsof the screen chassis in other embodiments.

Turning again to FIGS. 1 and 2, the screen assembly 100 having theplastic chassis 102 may be lighter than conventional screen assemblies,but still be structurally suitable for use in vibrating screeningmachines. The screen assembly 100 may be used for separation of solidsfrom a liquid (e.g. drill cuttings from drilling fluid), althoughembodiments are not limited to that particular application. For example,screen assemblies may also be used to separate different sizes ofsolids.

The screen assembly 100 has a generally rectangular shape with arectangular top face 101 and a rectangular bottom face 103, wherein thetop face 101 and the bottom face 103 are separated by a short distance.The distance between the top and bottom faces 101 and 103 may bereferred to as the thickness of the screen assembly 100. The size andthickness of the screen assembly 100 may vary. For example, the screenassembly may be approximately 25 inches wide by 49 and ¼ inches long by2 inches thick. However, other sizes may be used. For example, size mayvary based on the application and/or machine for which the screenassembly is intended. Thickness may also vary, for example, based on theproperties of the material(s) used in its composition, FEA requirements,the specification of the vibrating screening machine, the intendedapplication, etc. In addition, non-rectangular screen assemblies couldalso be used.

FIG. 3 is a bottom perspective view of the plastic chassis 102 shown inFIGS. 1 and 2. The plastic chassis 102 has first and second oppositeshort sides 106 and 108, and first and second opposite long sides 110and 112. The chassis 102 also has a first top face 114 and a secondbottom face 116. The terms “top” and “bottom” are used for ease ofreference herein and not to limit the orientation of the chassis 102.However, in normal operation, the top face 114 may face substantiallyupwards when the screen assembly 100 (shown in FIGS. 1 and 2) is mountedin a vibrating screen machine.

As seen in FIG. 3, the chassis defines a plurality of openings 120therethrough, from the top face 114 to the bottom face 116, which allowmaterial that has been screened to flow through the chassis 102. Forease of description, the direction parallel to the long sides 110 and112 will be referred to as longitudinal, and the distance between thelong sides 110 and 112 will be referred to as the width of the chassis102. The direction parallel to the short sides 106 and 108 will bereferred to as transverse, and the distance between the short sides 106and 108 will be referred to as the length of the chassis 102. Thedistance between the top face 114 and the bottom face 116 of the chassis102 will be referred to as the thickness of the chassis 102. Similardirections and dimensions will be used herein for other components andassemblies with similar rectangular shapes.

In this embodiment, the chassis 102 has a grid structure (between thefour sides 106, 108, 110 and 112 of the chassis 102) that defines theopenings 120 of the chassis 102. More specifically, the chassis 102includes a plurality of equally spaced apart ribs 126 in thelongitudinal direction and a plurality of equally spaced apart crossribs 122 and 124 in the transverse direction. In this embodiment, theribs 126 extend between the first and second short sides 106 and 108,and the cross ribs 122 and 124 extend between the first and second longsides 110 and 112. The ribs 126 and cross ribs 122 and 124 are parallelto the first face 114 and second face 116 of the chassis 102. Theexample ribs 126 and cross ribs 122 and 124 in this embodiment are inthe form of plastic beams with cross-sectional profiles that are talleror deeper than they are wide. However, the shape and structure of ribsand cross ribs may vary.

The ribs 126 and cross ribs 122 and 124 alternate between full-depthcross ribs 122 and partial-depth cross ribs 124 (where “depth” refers tothe vertical dimension of the cross ribs). The full-depth cross ribs 122have a depth approximately equal to the thickness of the chassis 102(i.e. extending from the top face 114 to the bottom face 116). Thepartial-depth cross ribs 124 on the other hand extend from the top face114 and only part of the way toward the bottom face 116. The ribs 126 inthis example also only extend part way from the top face 114 toward thebottom face 116. The short sides 106 and 108 of the chassis 102 act asadditional cross ribs in the grid structure.

In this embodiment, each of the cross ribs 124 and 126 includes atapered end 128 at the second long side 112 of the chassis, where thetapered ends 128 taper towards the top face 114 of the chassis. Thetapered ends 128 together give the second long side a sloped, taperedshape such that the top face 114 is wider than the bottom face 116.

It is to be understood that the grid structure of the chassis 102, andthe particular structure of the ribs 126 and cross ribs 122 and 124 isoptional, and the structure of the chassis may vary in differentembodiments. For example, rather than a grid of ribs and cross ribs, thechassis may define a plurality of round holes, or a plurality of longchannels extending substantially between two sides of the chassis.Embodiments are not limited to a particular configuration of openings inthe chassis. In the embodiment shown in FIG. 3, the first and secondshort sides 106 and 108 include first and second side walls 140 and 141respectively. The chassis includes 23 cross ribs 122 and 124 totalbetween the side walls 140 and 141, and five ribs 126 between the firstand second long sides 110 and 112. The side walls 140 and 141 alsofunction as cross ribs. The number of ribs and cross ribs in a gridstructure, as well as the depth and thickness of the ribs and cross ribsmay vary depending on the structural needs of the chassis and thematerial forming the chassis as well as other factors. The size andnumber of openings defined by the chassis may also vary. The specificembodiment shown in FIG. 3 is provided by way of example only.

FIG. 4 is a top plan view of the chassis 102 shown in FIGS. 1 to 3. FIG.4 shows the cross ribs 122 and 124 and the ribs 126. The chassis 102further includes a plurality of attachment points 130 distributed acrossthe top face 114 of the chassis 102 for attaching the metal screen 104(shown in FIG. 1). Several of the attachment points 130 are located atthe intersection of the ribs 126 and cross ribs 122 and 124. Otherattachment points 130 are near the short sides 106 and 108. Some of theattachment points 130 are provided on additional short ribs 132 thatextend a short distance inward from the short sides 106 and 110.

The metal screen 104 may be attached to the chassis by mechanical meanssuch as bolts, screws, rivets (e.g. plastic rivets), or using chemicaladhesive or other means, at the attachment points 130. For example, theattachment points may be holes configured to accept and hold screws, orholes for a rivet or holes to accept a threaded insert to which a boltor screw can be inserted, this would facilitate the re-use of thechassis to be refitted with a new screen. One possible means ofmechanical attachment is staking, in which plastic bosses from thechassis would extend through corresponding holes in the metal screen.Heat, sonic and/or mechanical means would then be used to melt or punchthe ends of the plastic bosses to deform the bosses and secure thescreen to the chassis. Any suitable means may be used to attach themetal screen to the chassis, and the attachment points 130 are shown byway of example only. Openings 120 of the example chassis 102 are alsovisible in FIG. 4.

FIG. 5 is a bottom plan view of the plastic chassis 102, again showingribs 126 and cross ribs 122 and 124.

FIG. 6 is a cross-section view of the chassis 102 taken along the lineB-B shown in FIG. 5. FIG. 7 is a cross-section view of the chassis 102taken along the line C-C shown in FIG. 5. The relative depths/heights ofthe full-depth ribs 122, the partial-depth ribs 124 and the ribs 126 areshown in FIGS. 6 and 7. In other embodiments, the cross ribs may allhave a uniform depth, possibly extending the full thickness of thechassis. Having at least some partial-depth ribs (such as partial-depthribs 124 in FIGS. 1 to 7) that do not extend all the way to the bottomface may have particular application to dual screen assemblies withscreens on the top and bottom faces of the chassis, as will be explainedin more detail below. For example, solids that pass through a topscreen, but are caught by the bottom screen may move under thepartial-depth ribs and/or cross ribs and out of a side of the chassis.Thus, the ribs and cross ribs may form channels (e.g. between thefull-depth cross ribs 122 of the chassis 102 shown in FIGS. 6 and 7) formaterial to move between the dual screens and out of an open side oroutlet of the assembly.

Screen assemblies are typically mounted to a screening machine by one ortwo sides of the screen assembly. For example, the screen assembly 100shown in FIGS. 1 and 2 may be mounted by clamping or wedging the firstand second short sides 106 and 108 of the chassis 102 into position.Thus, the long sides 110 and 112 may not be secured. The full-depthcross ribs 122 of the screen assembly 100 may provide more structuralstiffness and support than the partial-depth cross ribs 124 and the ribs126. The full-depth cross ribs 122 extending in the transverse directionmay provide structural support and resistance to warping in response tothe force applied to the short sides 106 and 108 from mounting theassembly 100.

FIG. 8 is an enlarged cross-section view of the portion of the chassis102 within circle E in FIG. 7. As seen in FIG. 8, the second short side108 of the chassis is shown. The short side 108 includes a wall 140(with an L-shaped cross-section in this example) that may act as amounting surface for mounting the screen assembly 100 (shown in FIGS. 1and 2) in a vibrating screening machine. The first short side 106 (shownin FIG. 3) has a corresponding structure. In other embodiments, one ormore sides do not include L-shaped side wall. For example, one or moresides may include two walls (e.g. ribs or cross ribs) close together(e.g. one inch apart) and joined by a series of short ribs or crossribs. Such a configuration is shown in FIG. 17 and discussed in detailbelow. Other configurations are also possible.

Turning again to FIGS. 1 and 2, the frame 142 of the metal screen 104 isgenerally aligned with and covers with the grid structure of the chassis102. The frame 142 includes an outer rectangular frame portion 143 withthe openings 144 therein. Although not shown in FIGS. 1 and 2, the metalscreen 104 includes a metal mesh (not shown) that covers the openings120 and 140 to screen material (e.g. slurry) that passes over the screenassembly 100. The mesh is not shown so that other components arevisible. Metal screen 104 is attached to the chassis 102 by fasteners146 (shown in FIG. 1) at attachment points 130 (shown in FIG. 4). Thefasteners may be bolts, screws, rivets, etc, to name a few examples. Anysuitable means for attaching the metal screen to the chassis may beused, and embodiments are not limited to any particular attachmentmethod.

The metal screen 104 is sized to cover the top face 114 of the chassis102 (shown in FIG. 4). The combination of the lightweight, stiff chassis102 with the metal screen 104 may provide a screen that weighs less thanconventional screens while still providing sufficient structuraldurability. The metal screen 104 may act as a sort of exoskeleton forthe chassis 102 that provides structural support and resistance to wear(from vibrations and/or material being screened) during normal operationof a vibrating screening machine.

FIGS. 1 and 2 also show optional end cover 105 that covers non-taperedcross rib ends 148. The metal screen 104 substantially covers the entiretop face 114 of the chassis 102 (shown in FIG. 3).

In use, as material (e.g. slurry) to be screened falls on metal screen104, larger solids are retained on the screen 104 while smaller solidspass through screen 104 and openings 144/120. The metal screen 104 mayprovide some protection and wear resistance (from the material beingscreened) for the chassis 102.

In some embodiments, the number of openings in the frame of the screenmay be different (more or less) than the number of openings in thescreen chassis. For example, in some embodiments, the frame of thescreen may include only one large opening (e.g. a single largerectangular opening) that at least partially overlays the openings ofthe screen chassis. In some embodiments, instead of a mesh, anotherscreening layer may be used (e.g. a perforated layer) to cover theframe. In other embodiments, the screen does not include a frame andmay, for example, be formed of a perforated plate (such as a perforatedmetal plate). For example, a perforated stainless steel plate could beused.

In some embodiments, the screen assembly may be convertible between asingle screen configuration and a dual screen configuration, where theassembly includes a second screen in the dual screen configuration. Forexample, the screen assembly 100 shown in FIGS. 1 and 2 may be convertedinto the dual screen assembly arrangement shown in FIG. 9.

For example, a metal screen may be placed on both the top face and thebottom face of the chassis. FIG. 9 is an exploded view of the screenassembly 100 from FIGS. 1 and 2, but with the addition of a second metalscreen 107 on the bottom face 116 of the chassis 102 (shown in FIG. 3).FIG. 9 shows the plastic chassis 102, the first metal screen 104discussed above, the end cover 105, and the second metal screen 107. Thefirst metal screen 104 is attached to the top face 114 of the chassis102, as described above. The second metal screen is attached to thebottom face 116 of the chassis 102 (shown in FIG. 3). The second metalscreen 107 is sized to fit over the bottom face 116, and has openings146 that align with the openings 120 in the chassis 102. As with thefirst metal screen 104, the second metal screen 107 includes a frame 111(generally aligned with the grid structure of the chassis 102) and amesh (not shown) covering the openings 146 for screening the material.It may be advantageous for the first, upper metal screen 104 to have alarger mesh size than the second, lower metal screen 107. That way,solids small enough to fit though the mesh of the first metal screen 104may still be screened by the second metal screen 104. Similarly, if aperforated plate rather than a frame and mesh is used for at least theupper screen, the upper screen may have a perforation size that isgreater than the mesh size or perforation size of the lower screen.

To convert the screen assembly 100 from the single screen configurationshown in FIGS. 1 and 2 to the dual screen configuration of FIG. 9, theend cover 105 may be removed and the lower metal screen 107 may beattached to the lower face 116 of the chassis 102. Thus, the assembly100 may be converted between single and dual screen configurations asneeded. The end cover 105 may be again placed on the assembly 100. Thus,in the single screen configuration, the lower metal screen 107 is notattached to the screen assembly 100, and in the dual screenconfiguration, the lower metal screen 107 is attached to the screenassembly 100.

The grid structure of the screen assembly 100 is bounded at three sides(i.e. has three closed sides). Specifically, the first and second sidewalls 140 and 141 form two closed sides (106 and 108). The first longside 110 is bounded or closed by the end cover 105. The second long side112 (with the tapered cross rib ends 128 as shown in FIG. 3) is open,such that debris caught between the first metal screen 104 and thesecond metal screen 105 may pass under the partial-depth ribs 124 andthe ribs 126 and exit out the second long end 112. The angled design ofthe second long side 112 (with the tapered rib ends 128 shown in FIG. 3)may allow debris between the two screens 104 and 107 to exit to anotherscreen assembly below. Some arrangements of dual screen assemblies arediscussed in International PCT Patent Application No. CA2014/000655filed Aug. 26, 2014, the entire content of which is incorporated byreference.

FIGS. 10 and 11 illustrate another dual screen assembly 200 according tosome embodiments. Like the screen assembly 100 shown in FIGS. 1, 2 and9, the screen assembly 200 may be converted between a single screenconfiguration and a dual screen configuration. A dual screenconfiguration is shown in FIGS. 10 and 11. FIG. 10 is a top perspectiveview of the screen assembly 200, and FIG. 11 is a bottom perspectiveview of the screen assembly 200. The screen assembly 200 includes a hardplastic chassis 202 that has a shape and structure similar to thechassis 102 shown in FIGS. 1 to 9. The screen assembly 200 also includesan end cover 203 (shown in FIG. 10) at a first long side 210, an uppermetal screen 204, a lower metal screen 205. As mentioned above,embodiments are not limited to the chassis being formed of hard plasticor screens/frames being formed of metal. The chassis 202 also includesfirst and second short side walls 206 and 208, which are opposite fromeach other. The side walls 206 and 208 together with the end cover 203bound three sides of the screen assembly. Opposite to the first longside 210 with the end cover 203 is an open second long side 212, whichis similar to the long side 112 of the screen assembly 100 shown inFIGS. 1 and 2. The upper metal screen 204 includes frame 207 (shown inFIG. 10) and mesh 239 covering the openings 220 and frame 207. The mesh239 is shown partially cut away in FIG. 10 to provide better visibilityof the frame 207. As explained above, other embodiments may use aperforated plate or another type of screening layer (other than a mesh).The lower metal screen 205 may be removable to convert the screenassembly 200 to a single screen configuration.

The grid structure formed by the chassis 202 (and the corresponding gridstructure of frame 207 of the upper metal screen 204) includes a seriesof ribs 126 and cross ribs 221. The ribs 226 are parallel to the longside wall 210 and are equally spaced apart between the long side wall210 and the open second long side 212. The cross ribs 221 are parallelto and equally spaced apart between the first and second side walls 206and 208. The cross ribs 221 include partial-depth ribs 222 andfull-depth ribs 224 as shown in FIG. 11, and similar to the chassis 102shown in FIGS. 1 to 9). The partial-depth ribs 222 and full-depth ribs224 alternate similar to the chassis 102 shown in FIGS. 1 to 9. The gridstructure defines openings 220. The cross ribs 221 and side walls 206and 208 include tapered ends 236, similar to the cross ribs 122 and 124of the screen assembly 100 shown in FIGS. 1 and 2.

The lower metal screen 205 in this embodiment includes a rectangularframe 231 defining openings 240 and includes mesh 241 covering the frame231 openings 240. The mesh 241 is also shown partially cut away in FIGS.11 and 12. Unlike the lower frame 105 shown in FIG. 9, the frame 231 ofthe lower metal screen 205 in this example includes more ribs 232compared to the chassis 202 and first metal screen 204. Specifically,the frame 231 of the lower metal screen 205 defines approximately sixribs 232 space apart between two long sides 249 and 250 of the frame.The frame 231 also includes cross ribs 234 that are generally alignedwith the cross ribs 221 of the chassis 202 and upper metal frame 204.The ribs 232 and cross ribs 234 of the lower metal screen form openings240 that will be covered by the mesh (not shown). The dual screenassembly 200 shown in FIG. 10 and 11 has fewer ribs 226 in the gridstructure formed by the chassis 202 and first metal screen 204 than thedual screen assembly example shown in FIG. 9. Again, the number andconfiguration (e.g. spacing, thickness, length, angle, etc.) of the ribsand cross ribs may vary in other embodiments based on several factors.

The upper metal screen 204 is attached to the chassis 202 at severallocations by screws 242 (shown in FIG. 10). The lower metal screen 205is similarly attached to the chassis 202 by several screws 244 (shown inFIG. 11). Other attachment means (e.g. bolts, rivets, adhesives,welding, etc.) may be used in other embodiments. The lower metal screen207 and the upper metal screen 204 may reinforce the chassis 202, likean exoskeleton, to provide a lightweight, sufficiently stiff screenassembly 200 suitable for vibrating screen machines.

FIG. 12 is a bottom plan view of the screen assembly 200 (including mesh241). The chassis 202, upper metal screen 204 and lower metal screen 205are visible. The open second long side 212 is also visible where debriscan exit from between the upper metal screen 204 and the lower metalscreen 205 in the area of the tapered rib ends 236.

FIG. 13 is a cross section view of the screen assembly 200 taken alongthe line A-A shown in FIG. 12. The chassis 202, end cover 203, uppermetal sheet 204 and lower metal sheet 205 are shown in FIG. 13. The lineA-A in FIG. 12 extends across the width of the screen assembly 200. Forpart of the length of line A-A, the line bisects a cross rib 221 alongits length, and then for the rest of the length of line A-A, it travelsparallel and adjacent to that cross rib 221. Thus, FIG. 13 shows apartial cross section of cross rib 221 as well as cross sections of tworibs 226.

FIG. 14 is an enlarged view of the portion of the screen assembly 200that is within the circle D in FIG. 13. FIG. 14 shows additional detailsof the end cover 203. The end cover includes a lower clamping section252 with a cross-section that is generally C-shaped and a hollow uppersection 254 with a rectangular cross section. The cross ribs 221 havecross rib ends 238 that are shaped to cooperate with the C-shaped lowerclamping section 252 of the end cover 203. Specifically, the cross ribends 238 include two small recesses 256 and 258 that the clampingsection 252 can grab to secure the end cover 203 to the chassis 202.

FIG. 14 also shows screws 242 and 244 that attach the upper metal screen204 and the lower metal screen 205 respectively to the chassis 202 inthis embodiment.

Referring again to FIGS. 10 and 11, the mesh 239 of the upper metalscreen 204 has a larger mesh size than the mesh 241 of the lower screen205. In use, as material or slurry to be screened falls on upper metalscreen 204, larger solids are retained on the upper metal screen 204while mid-size and smaller solids may pass through the openings 220 andfall onto lower metal screen 205. Since lower metal screen 205 has asmaller mesh size than upper metal screen 204, the solids that aresmaller enough to fit through upper metal screen 204, but too big topass through lower metal screen 205, may be retained on lower metalscreen 205. Smaller solids may pass through lower metal screen 205.Thus, the largest solids may be retained on upper metal screen 204,mid-size solids may be retained on lower metal screen 205 and thesmallest solids may pass through both screens 204 and 205. The mid-sizesolids retained on lower metal screen 205 can then be selectivelydirected in channels formed between the full-depth cross ribs 222 (andunder the partial-depth cross ribs 224 and ribs 226) and out of the openlong side 212.

FIGS. 15 and 16 are, respectively, top and bottom perspective views of asingle screen assembly 300 according to yet another embodiment. Thescreen assembly 300 includes a hard plastic chassis 302, an upper metalscreen 304 on a top face (shown in FIG. 17) of the chassis 302, and alower metal frame 305 on a bottom face (shown in FIG. 18) of the chassis302. Similar to embodiments described above, the assembly is rectangularin shape, and the upper metal screen 304 and the lower metal frame 305are sized to cover substantially the entire top and bottom faces of thechassis 302. As discussed above, embodiments are not limited to chassisformed of plastic, or screens formed of metal.

The chassis 302 has a grid structure defining openings 320, similar tothe chassis 102 and 202 discussed above with reference to FIGS. 1 to 14.The upper metal screen 304 in this embodiment includes a frame 307 thatdefines openings 340 that have approximately the same size/shape and arealigned with the openings 320 in the chassis 302. The lower metal from305 also defines a plurality of openings including small openings 342and large openings 344. The large openings are sized similar to theopenings 320 in the chassis 302, and each large opening 344 is alignedwith a corresponding opening 320 in the chassis 302. The small openings342 are approximately half the size of the openings 320 in the chassis302, and pairs of two small openings 342 are aligned with respectiveopenings 320 in the chassis 302.

The upper metal screen includes a mesh 309 (shown in FIG. 21) coveringthe openings 340 to screen material placed on the screen assembly 300.Another type of screening layer (rather than a mesh) or a perforatedplate (without a frame) may be used in other embodiments.

In the embodiment of FIGS. 15 and 16, the lower metal frame 305 does notinclude a mesh covering its openings in this embodiment and is providedfor structural support of the chassis. Material that passes through theupper metal screen 304 may pass through the openings 342 and 344 in thelower metal frame 305. The upper metal screen 304 and the lower metalframe 305 may act as an exoskeleton providing structural support andprovide protection/wear resistance for the plastic chassis 302.

The chassis 302 in this embodiment does not have an open side. Rather,the chassis has four closed sides 306, 308, 310 and 312, which functionas ribs/cross ribs in the grid structure.

FIG. 17 is a top plan view of the chassis 302 shown in FIGS. 15 and 16.The chassis 302 includes a first short side 306, a second short side 308opposite to the first short side 306, a first long side 310, and asecond long side 312 opposite to the first long side 310. The chassisincludes 23 cross ribs 322 parallel to and spaced equally between theshort sides 306 and 308. In this embodiment, each of the cross ribs 322is full-depth, extending the full thickness of the chassis 302 (similarto the cross ribs 122 of the chassis 102 shown in FIGS. 1 to 8). Thechassis 302 also includes a plurality of ribs parallel to and equallyspaced between the long sides 310 and 312. As shown in FIG. 24 anddiscussed below, the ribs 326 are partial-depth, extending only part wayfrom the top face 314 of the chassis 302 (similar to the ribs 126 of thechassis 102 shown in FIGS. 1 to 8).

The first short side 306 in this embodiment has an outer side wall 328and an inner side wall 330. In this embodiment the inner and outer sidewalls 328 and 330 of the first short side 306 are about one inch apart,although this distance is only provided by way of example and otherseparations may be used. The first short side 306 also defines aplurality of openings or hollows 332 between the outer facing surface328 and an inner facing surface 330. The inner side wall 328 and theouter side wall 330 essentially form cross ribs that are joined by shortribs 333 between the inner side wall 328 and the outer side wall 330.The inner side wall 328 and the outer side wall 330 and the short ribs333 thereby define the hollows 332. The hollows 332 extend from the topface 314 of the chassis 302 to the bottom face 316 shown in FIG. 18. Thesecond short side 308 has a structure that corresponds to the firstshort side 306. This structure may provide a relatively thick side wallwith the hollows 332 reducing overall weight. The first and second longsides 310 and 312 are walls that essentially form ribs have a thicknessapproximately equal to the thickness of the other ribs 326 and crossribs 322 of the chassis 102. The chassis 302 also includes a pluralityof additional short ribs 334 between the first short side 306 and thecross rib 322 closest to the side wall. Similar short ribs 335 arelocated at the second short side wall.

FIG. 17 also shows attachment points 346 on the top face 314 forattaching the upper metal screen 304 to the chassis 302. Similarattachment points 348 are defined on the bottom face 316 (shown in FIG.18) for attaching the lower metal frame 305.

Some example dimensions of the chassis 302 will now be described.However, it is to be understood that the dimensions are provided by wayof example only, and the chassis (including ribs, cross ribs, andchassis walls) may have different dimensions in other embodiments.

In the example of FIG. 17, the chassis is approximately 25 inches wideby 49.25 inches long by 2 inches thick. Other sizes are also possible.The ribs 326 and cross ribs 322 have an approximate thickness of 0.252inches. The attachment points 346 in this example are holes with aninner diameter of approximately 0.20 inches. The distance between theouter surface of the first short side 306 and the hollow portion 332 (asindicated by “d1” in FIG. 13) is 0.265 inches. The hollows 332 in thefirst and second short walls 306 and 308 may be spaced apart from eachother by approximately 0.215 inches. The second short 308 has acorresponding structure. As shown in FIG. 13, where an attachment point346 is not located on an intersection of the cross ribs 322 and ribs326, the width of the cross rib 322 around the attachment point widensfor form a generally circular bulge 350.

FIG. 18 is a bottom plan view of the chassis 302 shown in FIG. 17. Theattachment points 348 in bottom face 316 for attaching the lower metalframe 305 (shown in FIG. 16) are visible.

FIG. 19 is an enlarged partial cross sectional view of the chassis 302taken along the line D-D in FIG. 18. FIG. 19 shows more detail of theattachment points 346 in the upper face 314 and the attachment points348 in the lower face 316 of the chassis 302. It is to be understoodthat the details (dimensions, shapes, configuration etc.) of the crossrib 322 and attachment points 346 and 348 are exemplary and embodimentsare not limited to the specific details described below. The size, shapeand configuration of the cross ribs and attachment points may vary.

In this embodiment, the cross rib 322 has side walls 338 and 339, whichcurve around the attachment points 346 and 348 to form the circularbulge 350. The cross section of FIG. 19 is taken at the widest point ofthe circular bulge 350. As shown in FIG. 19, the attachment point 348 isin the form of a hole 352 having hole wall 354. The hole 352 is in theapproximate center of the circular bulge 350.

In this embodiment, the side walls 338 and 339 of the cross rib 322 areangled to each other by about 0.5 degree such that the cross rib 322slightly narrows or tapers from the top face 314 to the bottom face 316.This slight tapering or “draft” may be provided for molding purposes mayaid in ejection of the molded chassis from the mold. At the top face,the circular bulge 350 in the cross rib 322 has outer diameter “od1”,which is approximately 0.610 inches in this embodiment. At the bottomface, the circular bulge 350 has outer diameter “od2”, which isapproximately 0.580 inches. The hole 352 has a diameter “od3”, which isapproximately 0.160 inches at the top face 314 of the chassis 302. Thehole wall 354 is angled such that the hole 352 slightly narrows as itextends into the chassis 302 from the top face 314, and the hole 352 hasa diameter of approximately 0.148 inches near its bottom 356. The hole352 is approximately 0.754 inches deep in this example. The hole 352 isshaped for receiving a bolt or rivet (not shown in FIG. 18) to attachthe upper metal screen 304 (shown in FIG. 15) to the chassis 302. At thetop face 314, the distance “d1” from the circumference of the hole 352to the circumference of the circular bulge 350 is approximately 0.225inches. The attachment point 348 at the lower face 316 is similar to theattachment point 346 in the upper face discussed above.

FIG. 19 also shows, using stippled lines, the thickness “d2” of thelower metal frame 307. In this embodiment, the thickness d2 is 0.075inches. A bolt (not shown) that is 0.75 inches long may be received inattachment point 348 to attach the lower metal screen 307 to the chassis302. The upper metal screen 304 may similarly be attached to the upperface 314. With reference again to FIGS. 17 and 18, the plurality ofattachment points 346 and 348, together with corresponding bolts, screwsor rivets, may securely attach the upper metal screen 304 and the lowermetal frame 307 to the chassis.

FIG. 20 is a side view of the chassis 302 showing the first long side310. The thickness of the chassis is indicated by “d3” in FIG. 20. Inthis embodiment, the chassis is approximately 2 inches thick. The shortside 308 is at a slightly acute angle “α” from the bottom top face 314.The angle α in this example is approximately 89.5 degrees. This angle(i.e. draft) may allow the chassis 302 to be more easily ejected from amold when formed.

FIG. 21 is a top plan view of the upper metal screen 304 showing theframe 307 of the metal screen and the mesh 309. The mesh 309 ispartially cut away so that the frame 307 is also visible. However, themesh 309 will cover all of the openings 340 of the frame 307 forscreening material that falls on the screen 304. The mesh size of themesh 309 may vary and may depend on the type of material to be screened.Similarly, for embodiments using a perforated plate (rather than a frameand mesh type screen), the perforation size may depend on the type ofmaterial being screened. In FIG. 21, holes 360 are defined in the frame307, and the holes 360 are arranged to align with the attachment points346 in the upper face 314 of the chassis 302 (shown in FIG. 17). Theholes 360 in this embodiment receive bolts or rivets to secure the uppermetal screen 304 to the chassis 302. However, any suitable method forattaching a metal screen to a chassis may be used.

The frame 307 of the upper metal screen 304 has a grid structure that isaligned with the chassis 302 shown in FIG. 17. The openings 340 in theframe 307 aligned with the openings 320 of the chassis 302.

The frame 307 of the upper metal screen 304 may be manufactured, forexample, from sheet metal. For example, the sheet metal may be cut toform a rectangle that has the same size as the top face 314 of thechassis 302, and the openings 340 and holes 360 may be cut in the sheetmetal. The openings 340 and holes 360 could also be cut before or at thesame time as the outer rectangle shape of the frame 307.

In some embodiments, sheet metal for a frame of a screen or a perforatedplate may be cut and folded along its edges so that it covers one ormore sides or ends of the chassis as well as the top or bottom face ofthe chassis. This folding of the sheet metal could cover substantiallycover each side of the chassis for a single screen embodiment, forexample. For a dual screen embodiment, three sides of the chassis couldbe covered by the sheet metal, with an open side not covered by thesheet metal so that material can still exit through the open side. Byfolding the sheet metal to cover one or more sides of the chassis, theoverall structural strength of the screen assembly may be improved.

FIG. 22 is a bottom plan view of the lower metal frame 305 that is to beattached to the bottom face 316 of the chassis 302 shown in FIG. 18. Thelower metal frame 305 may also be manufactured from sheet metal, forexample. The lower metal frame 307 includes large openings 342 and small344. The large openings 342 are generally aligned with openings 320 ofthe chassis 302 that are nearest the long sides 310 and 312 of thechassis 302 (shown in FIG. 16). The frame 307 has a grid structure that,in comparison to the chassis 302, includes two additional ribs 362 and363 that, when attached to the chassis 302, are spaced between the threecenter most cross ribs 322 of the chassis 302, thereby creating thesmaller openings 344. The small openings 344 are aligned such that pairsof small openings 344 cover respective single openings 320 of thechassis 302. The size and/or arrangement of the openings on the lowermetal screen may vary in some embodiments. By including smalleropenings, the structural strength/stiffness provided by the lower metalscreen may be improved. Thus, the design of the lower metal screen mayvary depending on the required structural strength/stiffness requiredfor a particular application. The lower metal frame 305 also definesholes 366 that are arranged to align with the attachment points 348 inthe lower face 316 of the chassis 302 (shown in FIG. 18). The holes 366in this embodiment receive bolts or rivets to secure the lower metalframe 305 to the chassis 302. However, any suitable method for attachinga metal frame to a chassis may be used, as explained above.

FIG. 23 is a top plan view of the assembled screen assembly 300. In FIG.18, the mesh 309 is shown, but is again cut away to show othercomponents of the screen assembly 300, including the metal frame 307 ofthe upper metal screen 304 and the lower metal frame 305. Bolts 368attaching the upper metal screen 304 to the chassis 302 are also shownin FIG. 23.

FIG. 24 is a cross section side view of the screen assembly 300 takenalong the line L-L in FIG. 23. Cross sections of the cross ribs 322 arevisible, as are the ribs 326. As seen, the ribs 326 extend from the topface 314 of the chassis 302 and only part way to the bottom face,whereas the cross ribs 322 extend fully between the top face 314 andbottom face 316, thereby having a depth that equals the thickness of thechassis 302.

FIG. 25 is a cross section top view of the screen assembly 300 takenalong the line P-P in FIG. 24. The line P-P in FIG. 23 is below thelevel of the ribs 326. Thus, the cross ribs 322, but not the ribs 326,of the chassis 302 are visible in FIG. 25. FIG. 25 also shows the lowermetal frame 305.

FIG. 26 is a cross section bottom view of the screen assembly 300 takenalong the line R-R in FIG. 24. The ribs 326 and cross ribs 322 of thechassis 302 are visible in FIG. 26. FIG. 26 also shows the upper metalscreen 304 including the mesh 309.

As with frames for metal screens, the configuration of lower metalframes (without a mesh or other screening layer) for screen assembliesmay vary. FIG. 30 is a top view of a lower metal frame 380, according toanother embodiment, that could be attached to a bottom face of achassis. For example, the frame 380 could be attached to the bottom face316 of the chassis 302 shown in FIGS. 15 to 20 and 23 to 26 rather thanthe lower metal frame 305. The lower metal frame 380 shown in FIG. 30has first and second opposite short sides 381 and 382 and first andsecond opposite long sides 383 and 384. The lower metal frame 380 has agrid structure including longitudinal ribs 385 that extend between thefirst and second short sides 381 and 382. The grid structure alsoincludes a first set of several cross ribs 386 that are angledapproximately 60 degrees to the ribs, and a second set of several crossribs 387 that are angled approximately 60 degrees to the ribs (in theopposite direction) and to the first set of cross ribs 386. Thisarrangement of ribs 385 and cross ribs 386 and 387 defines severaltriangle shaped openings 388 and several diamond shaped openings 390.The openings 388 and 390 may allow screened material to pass throughfrom the chassis. Depending on the structure of the screen chassis towhich the lower metal frame 380 is attached, the openings 388 and 390may or may not be aligned with openings of the screen chassis. The lowermetal screen 380 also includes attachment points 392 (e.g. holes forscrews, bolts etc.) for facilitating attachment to a screen chassis. Thelower metal screen 380 may be attached to a screen chassis using anysuitable means. The grid structure of the lower metal screen 380 mayprovide structural support for a screen assembly when attached to achassis. A similar grid structure may also be used for the frame of ametal screen (upper or lower) in some embodiments.

In some embodiments, multiple screen and chassis may be stacked suchthat three or more screens (possibly with different mesh sizes) may beused in a cascading manner. FIG. 27 is an exploded view of a stackedscreen assembly 400 according to one example embodiment. The stackedscreen assembly includes a first chassis 402, a second chassis 404, anda third chassis 406. Each chassis has a rectangular shape (andthickness) that is similar to the chassis discussed above. However, theshape of the screen assemblies in other embodiments may vary. Thestacked screen assembly 400 also includes a first screen 408, a secondscreen 410 and a third screen 412.

In this embodiment, each of the chassis 402, 404 and 406 is made of hardplastic (although plastic is not required in all embodiments). The firstchassis 402 and the second chassis 404 have a channel design.Specifically, with reference to the first chassis 402, the chassis 402defines multiple long channels 414 between arms or extensions 416. Theextensions 416 have a depth equal to the thickness of the chassis 402.The first chassis 402 also has three closed sides 418, 420 and 421 andone opened side 422. The second chassis 404 has the same structure asthe first chassis 402, defining channels 424 and having one open side426. The third chassis 406 also defines channels 427, but has fourclosed sides 428, 430, 432 and 433 (and no open side). Thearms/extensions 416 have rectangular cross sectional profile in thisexample, but other shapes are also possible (e.g. circular profile).

Each of the first, second and third screens 408, 410 and 412 has arespective frame (not shown) and a respective mesh 434, 436 and 438covering the frame. The frames are shaped for mounting the first, secondand third screens 408, 410 and 412 on the first, second and thirdchassis 402, 404 and 406 respectively. The frames also have openings(not shown) that are aligned with the chassis 402, 404 and 406. The mesh434 of the first screen 406 may have the largest mesh size, and thethird screen 412 may have the smallest mesh size.

FIG. 28 shows the assembled stacked screen assembly 400, with thefollowing components in order from the top: first screen 408, firstchassis 402, second screen 410, second chassis 404, third screen 412,and third chassis 406. Any suitable fastening means (e.g. bolts, screws,rivets, welding, adhesives, etc.) may be used to connect the screens(408, 410, 412) and the chassis (402, 404, 406) together.

In use, solution (e.g. slurry) of mixed solids and liquid may fall onthe screen in a vibrating machine. The largest solids may be caught bythe first screen 408, with remaining solids and liquid may flow downthrough the channels 414 (shown in FIG. 27) of the first chassis 402 andonto the second screen 410. The second screen may filter medium sizedsolids, which may then travel through the channels 414 and exit throughthe open side 422 of the first chassis 402. The remaining solids thatare not filtered out by the second screen 410 and the liquid may passthrough the second screen 410 and onto the third screen 412. The thirdscreen 412 may then filter out smaller solid solids, which will thenexit via the open side 426 of the second chassis 404. Finally, theliquid and solids small enough to pass through the mesh 438 of the thirdscreen 412 may exit through the channels 426 (shown in FIG. 27) of thethird chassis 406.

In some embodiments, a fourth screen (not shown) could be placed on abottom face of the third chassis 406. In such embodiments, the thirdchassis could be modified to include an open side, similar to the firstand second chassis 402 and 404 to allow screened solids to exit throughthe open side.

The stacking pattern shown in FIGS. 27 and 28 could include additionalchassis and/or screens. Stacked screen assemblies are not limited tothree chassis and three screens, and more or fewer chassis and screensmay be used in other embodiments. In addition, a chassis with channels(such as first chassis 402 shown in FIG. 27) may be used in the singleand/or dual screen models described above with reference to FIGS. 1 to27. Conversely, a stacked screen assembly could use one or more chassiswith a grid structure (such as the chassis 102 shown in FIG. 3, or thechassis 302 shown in FIGS. 16 and 17). Other chassis arrangements mayalso be used.

A stacked configuration (such as the embodiment of FIGS. 27 and 28) maybe used for situations where solids (such as particles) are to beseparated in two or more different sizes. The stacking shown in FIGS. 27and 28 may also be repeated with additional screens and/or chassis asneeded to provide the desired number of different separations.

Some embodiments of the screen assemblies described herein may berelatively lightweight and/or stiff, which may result in the screenbeing more wear resistant (resulting in increased longevity) compared toconventional screen assemblies. For example, the screen assembly of someembodiments may be less prone to center-screen vibrations at frequenciesand/or amplitudes higher than the vibrating frequency of the machine. Inorder to compensate for typical wear and damage problems, someconventional screen assemblies may be rotated up to 90 degrees to thedirection of material flow. One or more embodiments described herein mayavoid the need for such rotation to reduce wear or increase the lifetimeof the screen assembly compared to conventional screen assemblies. Someembodiments of the screen assemblies described herein may be costeffective to manufacture. Some embodiments may by recyclable. Forexample, the mechanical attachment means for attaching the screen(s) tothe chassis may allow the screen and chassis to be separated forrecycling purposes and/or to be reused with a new screen(s).

Some embodiments of the disclosure provide a method for producing ascreen assembly (such as the example assemblies described above). FIG.29 is a flowchart of an example method according to some embodiments. Atblock 2902, a screen chassis is provided. The screen chassis comprises afirst face and a second face opposite to the first face, the screenchassis defining a plurality of openings therethrough from the firstface to the second face for allowing passage of a screened material. Thescreen chassis may, for example, be in the form of any example chassisdescribed above (e.g. chassis 102, 202, 302, 402, 404 or 406 shown inFIGS. 3, 10, 17, 18 27 and 28). At block 2904, a screen is provided. Thescreen may be formed of metal as described above. The screen includes aframe and a mesh, the frame comprising a plurality of openings that arealigned with the openings of the screen chassis, and the mesh coveringthe openings of the frame. The screen may, for example, be in the formof any of the example metal screens described above (e.g. metal screens104, 107, 204, 205, 304, 408, 410 or 412 shown in FIGS. 1, 2, 9, 10, 11,15, 16, 21, 22, 27 and 28). At block 2906, the screen is attached to thescreen assembly such that the metal screen covers the openings in thescreen chassis. The screen may be attached in any suitable mannerdescribed above.

Providing the screen chassis may include manufacturing, purchasing, orotherwise obtaining the screen chassis. The screen chassis may be moldedfrom a lightweight, stiff material including, but not limited toplastic.

Providing the screen may include manufacturing, purchasing, or otherwiseobtaining the screen. For example, the screen may be at least partiallymanufactured from sheet metal (e.g. using a sheet metal punchingprocess) as described above. More particularly, the screen may include aframe and/or perforated plate that is formed by a sheet metal punchingprocess

The method may further include providing and/or attaching a secondscreen to the screen chassis on a face of the screen chassis that isopposite from the first metal screen. The attaching may be accomplishedby any suitable means, as described above. The second screen may beattached to the second face of the screen chassis such that the screencovers the openings in the screen chassis at the second face.

In some aspects, any of the screen chassis described above may beprovided separately from the metal screen. For example, some embodimentsprovide a screen chassis for attaching to a metal screen for use in avibratory screen machine. The screen chassis may, for example, be in theform of any of the chassis 102, 202, 302, 402, 404 or 406 shown in FIGS.3, 10, 17, 18 27 and 28.

In some aspects, any of the metal screens and/or metal frames discussedabove may be provided separate from the screen chassis. In someembodiments, there is provided a metal screen for attaching to and atleast partially covering a screen chassis for use in a vibratory screenmachine, the metal screen may, for example, be in the form of any of themetal screens 104, 107, 204, 205, 304, 408, 410 or 412 shown in FIGS. 1,2, 9, 10, 11, 15, 16, 21, 22, 27 and 28.

In some embodiments, the metal screen(s) may be removable from thechassis such that multiple screens may be swapped or replaced as needed,while still using the same screen chassis. Similarly, the chassis may bereplaceable. For example, removable attachment means such as screws orbolts could be used to facilitate screen replacement. This capabilitymay not be provided by conventional screens. In some dual screenembodiments, the screen on a top face of a chassis may include arelatively durable perforated plate and/or mesh material for screeningthe material. Such durable perforated plates or mesh materials mayoutlast the lower screen material and possibly the screen chassisitself. The top screen comprising the more durable (and possiblyexpensive) material could then be used with a replacement screen chassisand/or lower screen. Some perforated plates can cost several thousanddollars and some screen treating materials (e.g. DLC and ion nitriding)may also be expensive. Thus, the reusable, and recyclable nature of thescreen assemblies described herein could reduce the cost of using suchexpensive materials since the expensive components may be reused whenother less expensive components wear out.

It is to be understood that a combination of more than one of the aboveapproaches may be implemented in some embodiments. Embodiments are notlimited to any particular one or more of the approaches, methods orapparatuses disclosed herein. One skilled in the art will appreciatethat variations, alterations of the embodiments described herein may bemade in various implementations without departing from the scopethereof. It is therefore to be understood that within the scope of theappended claims, the disclosure may be practiced otherwise than asspecifically described herein.

What has been described is merely illustrative of the application of theprinciples of the invention. Other arrangements and methods can beimplemented by those skilled in the art without departing from the scopeof the present invention.

The invention claimed is:
 1. A screen assembly for a vibrating screeningmachine, the screen assembly comprising: a screen chassis comprising afirst face and a second face opposite to the first face, the screenchassis defining a plurality of openings therethrough from the firstface to the second face for allowing passage of a material that has beenscreened; a first screen for screening the material, the screen beingattached to the first face of the screen chassis and covering theopenings of the screen chassis at the first face; and a second screenfor screening the material, the second screen being attached to thesecond face of the screen chassis and covering the openings of thescreen chassis at the second face; wherein the first screen has a firstmesh size or perforation size, and the second screen has a second meshsize or perforation size.
 2. The screen assembly of claim 1, wherein atleast one of the first or second screen comprises a perforated plate. 3.The screen assembly of claim 2, wherein the perforated plate is formedfrom sheet metal.
 4. The screen assembly of claim 1, wherein at leastone of the first or second screen comprises a frame and a screeninglayer, the frame defining at least one opening, the at least one openingat least partially overlaying the openings of the screen chassis, theframe being attached to the screen chassis, the screening layer coveringthe at least one opening of the frame.
 5. The screen assembly of claim4, wherein the screening layer comprises a mesh.
 6. The screen assemblyof claim 4, wherein the at least one opening of the frame comprises aplurality of openings that are aligned with the openings of the screenchassis.
 7. The screen assembly of claim 4, wherein the screen comprisesmetal.
 8. The screen assembly of claim 7, wherein the frame is formedfrom sheet metal.
 9. The screen assembly of claim 1, wherein the screenchassis comprises one or more of: plastic; aluminum; steel; and acomposite material.
 10. The screen assembly of claim 1, wherein thescreen chassis is formed by a molding process.
 11. The screen assemblyof claim 1, wherein the first face of the screen chassis facessubstantially upward when the screen assembly is mounted in thevibratory screening machine.
 12. The screen assembly of claim 1, whereinthe screen chassis comprises a grid structure defining the plurality ofopenings in the screen chassis.
 13. The screen assembly of claim 12,wherein the grid structure of the screen chassis comprises a pluralityof ribs parallel to the first and second faces, and a plurality of crossribs parallel to the first and second faces and perpendicular to theribs.
 14. The screen assembly of claim 13, wherein one or more of theribs or cross ribs extend between the first face and the second face ofthe screen chassis.
 15. The screen assembly of claim 14, wherein one ormore of the ribs and cross ribs extend only part way from the first faceof the screen chassis toward the second face.
 16. The screen assembly ofclaim 13, wherein screen comprises a frame and the frame of the screencomprises a grid structure that is aligned with the grid structure ofthe screen chassis.
 17. The screen assembly of claim 15, wherein the oneor more of the ribs and cross ribs extending only part way from thefirst face of the screen chassis toward the second face allow passagethereunder of solids caught by the second screen, and the one or more ofthe ribs or cross ribs extending between the first face and the secondface of the screen chassis form channels therebetween for passage of thesolids caught by the second screen.
 18. The screen assembly of claim 1,wherein the first mesh size or perforation size is different than thesecond mesh size or perforation size.
 19. The screen assembly of claim18, wherein the first mesh size or perforation size is larger than thesecond mesh size or perforation size.
 20. The screen assembly of claim1, wherein at least one of the first or second screen is removablyattached to the screen chassis such that the screen or the screenchassis is replaceable.
 21. The screen assembly of claim 1, the screenchassis being a first screen chassis, and the screen assembly furthercomprising at least one additional screen chassis having openingstherethrough, the first screen chassis and the at least one additionalscreen chassis being in a stacked formation with the openings of thefirst screen chassis being aligned with the openings of the at least oneadditional screen chassis, the screen assembly further comprising, foreach pair of adjacent screen chassis, a respective additional screen,for screening the material, between the pair of adjacent screen chassis.22. A screen assembly for a vibrating screening machine, the screenassembly comprising: a screen chassis comprising a first face and asecond face opposite to the first face, the screen chassis defining aplurality of openings therethrough from the first face to the secondface for allowing passage of a material that has been screened; a firstscreen for screening the material, the screen being attached to thefirst face of the screen chassis and covering the openings of the screenchassis at the first face; and a second screen for screening thematerial, the second screen being attached to the second face of thescreen chassis and covering the openings of the screen chassis at thesecond face; wherein the second screen comprises a frame defining atleast one opening; and a mesh covering the at least one opening of theframe.
 23. A screen assembly for a vibrating screening machine, thescreen assembly comprising: a screen chassis comprising a first face anda second face opposite to the first face, the screen chassis defining aplurality of openings therethrough from the first face to the secondface for allowing passage of a material that has been screened; a firstscreen for screening the material, the screen being attached to thefirst face of the screen chassis and covering the openings of the screenchassis at the first face; and a second screen for screening thematerial, the second screen being attached to the second face of thescreen chassis and covering the openings of the screen chassis at thesecond face; wherein the screen chassis defines a plurality of channelsallowing solids caught by the second screen to move through thechannels.
 24. The screen assembly of claim 23, further comprising atleast one open side allowing said solids caught by the second screen toexit from of the at least one open side.
 25. A screen assembly for avibrating screening machine, the screen assembly comprising: a screenchassis comprising a first face and a second face opposite to the firstface, the screen chassis defining a plurality of openings therethroughfrom the first face to the second face for allowing passage of amaterial that has been screened; a first screen for screening thematerial, the screen being attached to the first face of the screenchassis and covering the openings of the screen chassis at the firstface; and a second screen for screening the material, the second screenbeing attached to the second face of the screen chassis and covering theopenings of the screen chassis at the second face; wherein the secondscreen is removably attached to the screen chassis such that the screenassembly has a single screen configuration in which the second screen isnot attached to the screen assembly, and a dual screen configuration inwhich the second screen is attached to the screen assembly.
 26. A screenassembly for a vibrating screening machine, the screen assemblycomprising: a screen chassis comprising a first face and a second faceopposite to the first face, the screen chassis defining a plurality ofopenings therethrough from the first face to the second face forallowing passage of a material that has been screened; a first screenfor screening the material, the screen being attached to the first faceof the screen chassis and covering the openings of the screen chassis atthe first face; and a second screen that is removably attachable to thesecond face of the screen chassis such that the second screen covers theopenings of the screen chassis at the second face and such that thescreen assembly has a single screen configuration in which the secondscreen is not attached to the screen assembly, and a dual screenconfiguration in which the second screen is attached to the screenassembly.
 27. A screen assembly for a vibrating screening machine, thescreen assembly comprising: a screen chassis comprising a first face anda second face opposite to the first face, the screen chassis defining aplurality of openings therethrough from the first face to the secondface for allowing passage of a material that has been screened; a screenfor screening the material, the screen being attached to the first faceof the screen chassis and covering the openings of the screen chassis atthe first face; and a frame attached to the second face of the screenchassis, the frame attached to the second face defining at least oneopening at least partially overlaying the openings of the screen chassisat the second face.